Maltitol is a sugar alcohol obtained through catalytic hydrogenation of maltose. Its sweet taste and degree of sweetness are similar to those of sucrose, and since it is hardly utilized by oral bacteria, it does not cause a tooth decay. It is hardly digested by human digestive enzymes, is stable against the heat, and does not promote insulin secretion. It also has a beneficial effect on the absorption of various minerals, and other desirable functions.
Crystalline maltitol and crystalline mixture solid containing it are widely used as materials in foods, pharmaceuticals, and cosmetics due to their low hygroscopicity and excellent performance as an excipient.
Method for manufacturing crystalline maltitol is disclosed in (1) Japanese TOKKYO-KOKAI-KOHO (18-month Publication of Unexamined Patent Application) SHOWA 57(1982)-134498 (hereinafter referred to as TOKKAISHO 57134498),(2) Japanese TOKKYO-KOKOKU-KOHO(Publication after Examination for Opposition) HEISEI 2(1990)-11599 (hereinafter referred to as TOKKOHEI 2-11599), and (3) Japanese TOKKYO-KOKAI-KOHO (18-month Publication of Unexamined Patent Application) SHOWA 61(1986)-180795 (hereinafter referred to as TOKKAISHO 61-180795).
In the method in (1), an underground starch such as potato starch is liquefied, saccharified, purified, and the maltose crystallized in order to prepare high-purity maltose with a solids maltose content of 93 to 100% by weight in the solid component. This product is then subjected to catalytic hydrogenation to convert it to high-purity maltitol, which is then crystallized to manufacture crystalline maltitol.
In the method in (2), maltose syrup with a maltose content of 50 to 80% by weight in the solid component is subjected to catalytic hydrogenation to convert it to the corresponding maltitol syrup, which is then subjected to chromatographic separation to obtain a fraction with a maltitol content of 87% by weight or more in the solid component. This is concentrated and crystallized to manufacture crystalline maltitol.
In the method in (3), maltose syrup with a maltose content of 50% by weight or more in the solid component is subjected to catalytic hydrogenation, and then subjected to chromatographic separation to simultaneously obtain (i) a fraction which has maltitol as its principal component and which is useful as a raw material for the manufacture of crystalline maltitol and crystalline mixture solid containing this, and (ii) a fraction having maltotriitol as its principal component.
(1) above also discloses methods for manufacturing crystalline mixture solid containing crystalline maltitol using known methods such as block grinding method, fluidized granulation, and spray drying from a maltitol massecuite. PA1 1) the first step of hydrogenating syrup having a maltose content of 40 to 75% by weight in the solid component under the existence of catalyst to obtain corresponding syrup of sugar alcohol; PA1 2) the second step of chromatographically separating said syrup of sugar alcohol by supplying said syrup of sugar alcohol to a column packed with a cation exchange resin to obtain high sorbitol content fraction, maltitol syrup fraction (a) having a maltitol content of 80.5 to 86.5% by weight in the solid component and polyol fraction whose degree of polymerization (DP) is 3 or more; PA1 3) the third step of chromatographically separating said maltitol syrup fraction (a) by supplying said maltitol syrup fraction (a) to a column packed with a cation exchange resin to obtain high sorbitol content fraction, maltitol syrup fraction (b) having a maltitol content of 97.5% by weight or more in the solid component and polyol fraction whose degree of polymerization (DP) is 3 or more; PA1 4) the fourth step of crystallizing after a concentration of said maltitol syrup fraction (b) and separating crystalline maltitol from mother liquor having a maltitol content of 90% by weight or more in the solid component, and PA1 5) the fifth step of spray-drying or kneading under cooling the mother liquor obtained in the fourth step in the presence of a seed crystal to obtain crystalline mixture solid containing crystalline maltitol. PA1 1) the first step of hydrogenating syrup having a maltose content of 40 to 75% by weight in the solid component under the existence of catalyst to obtain corresponding syrup of sugar alcohol; PA1 2) the second step of chromatographically separating said syrup of sugar alcohol by supplying said syrup of sugar alcohol to a column packed with a cation exchange resin to obtain high sorbitol content fraction, maltitol syrup fraction (a) having a maltitol content of 80.5 to 86.5% by weight in the solid component and polyol fraction whose degree of polymerization (DP) is 3 or more; PA1 3) the third step of chromatographically separating said maltitol syrup fraction (a) by supplying said maltitol syrup fraction (a) to a column packed with a cation exchange resin to obtain high sorbitol content fraction, maltitol syrup fraction (b) having a maltitol content of at least 97.5% by weight in the solid component and polyol fraction whose degree of polymerization (DP) is 3 or more; PA1 4) the fourth step of concentrating said maltitol syrup fraction (b) and then spray-drying or kneading under cooling it in the presence of a seed crystal. PA1 1) the first step of hydrogenating syrup having a maltose content of 40 to 75% by weight in the solid component under the existence of catalyst to obtain corresponding syrup of sugar alcohol; PA1 2) the second step of chromatographically separating said syrup of sugar alcohol by supplying said syrup of sugar alcohol to a column packed with a cation exchange resin to obtain high sorbitol content fraction, maltitol syrup fraction (a) having a maltitol content of 80.5 to 86.5% by weight in the solid component and polyol fraction whose degree of polymerization (DP) is 3 or more; PA1 3) the third step of chromatographically separating said maltitol syrup fraction (a) by supplying said maltitol syrup fraction (a) to a column packed with a cation exchange resin to obtain high sorbitol content fraction, maltitol syrup fraction (b) having a maltitol content of 97.5% by weight or more in the solid component and polyol fraction whose degree of polymerization (DP) is 3 or more; PA1 4) the fourth step having a sub-step of crystallizing, in the presence of a seed crystal, a part of the syrup resulting from a concentration of said maltitol syrup fraction (b) to separate crystalline maltitol from mother liquor having a maltitol content of 90% by weight or more in the solid component, and another sub-step of spray-drying or kneading under cooling, in the presence of a seed crystal, remaining part of the syrup resulting from a concentration of said maltitol syrup fraction(b) to obtain crystalline mixture solid containing crystalline maltitol. PA1 5) the fifth step of spray-drying or kneading under cooling the mother liquor obtained in the fourth step in the presence of a seed crystal to obtain crystalline mixture solid containing crystalline maltitol.
However, these conventional methods have numerous problems and are not satisfactory as methods for the manufacture on an industrial scale of crystalline maltitol and crystalline mixture solid containing this.
For example, in the manufacturing method in (1), in the step of liquefying starch a solution having a low DE (dextrose equivalent) needs to be preliminary produced to be saccharified in order to prepare high-purity maltose. In the usual concentration, the liquid has an extremely high viscosity, so it is necessary to conduct liquefaction and saccharification at low concentrations. This requires that large volumes of water be evaporated during the concentration process, and that large amounts of enzymes be used during saccharification. It is also necessary to use isoamylase, which is expensive.
Further, in order to maintain maltitol purity during catalytic hydrogenation, it is necessary to conduct the process while using large quantities of catalyst under mild temperature conditions in order to prevent decomposition of the maltose and maltitol. This is disadvantageous from an economic standpoint.
With the method in (1), the limit of the purity of the maltose obtainable through saccharification is usually about 90 to 93%, and, accordingly, the large quantities of mother liquor produced through crystallization of the maltitol obtained by catalytic hydrogenation have a low maltitol content, making it difficult to recrystallize maltitol from the mother liquor, or to manufacture crystalline mixture solid containing this. Accordingly, the method produces large amounts of a mother liquor which is suitable only for use as liquid products, such as hydrogenated maltose syrup, hydrogenated starch hydrolysates and the like having a lower added value than crystalline maltitol.
With the manufacturing methods in (2) and (3), the syrup containing maltose of about 50 to 80% by weight, which is ordinarily used as the raw material, also contains large quantities of glucose and oligosaccharide. Accordingly, after completing catalytic dehydrogenation, when it is attempted to obtain a maltitol fraction of high purity in a single chromatographic separation, the recovery rate, that is, productivity, is poor; conversely, when it is attempted to raise productivity, the maltitol content of the fractionated liquid declines, making it difficult to ultimately crystallize the maltitol.
Particularly with the method in (2), since the mother liquor separated in crystallization is returned to the chromatographic separation process in order to raise crystalline maltitol productivity, an oligosaccharide fraction whose DP is 3 or more, a product with virtually no utility value, is ultimately produced in the chromatographic separation process.
With the method in (2), when the mother liquor is returned to the chromatographic separation process, the sugar composition of the mother liquor is significantly affected by the outcome of starch saccharification and the condition of crystallization of the crystalline maltitol, so a rather complex operating management is required to obtain fractions of a certain maltitol purity during the chromatographic separation process.
With the method in (1), even where crystalline mixture solid containing crystalline maltitol are manufactured using such common methods as block grinding method, fluidized granulation, and spray drying from a maltitol massecuite, the economic disadvantages of the method are already apparent at the maltose preparation stage.
With the foregoing in view, it is an object of the present invention to overcome the problems outlined above to provide a method for the economical manufacture of high-value added crystalline maltitol and crystalline mixture solid containing this.